1. Field of the Invention
The present invention relates to a water-based ink (hereinafter simply referred to as “ink”) for ink-jet recording.
2. Description of the Related Art
In an ink-jet recording method, recording is performed by generating fine droplets of ink according to various ink ejection methods, causing them to fly, and allowing the ink to adhere to a recording material such as paper. In such a case, the ink droplets are generated by an ink ejection method such as: an electrostatic attraction method by means of the application of high voltage; a drop-on-demand method in which mechanical vibrations or displacements are applied to ink by use of a piezoelectric element; or a thermal method which utilizes the pressure generated when the ink is heated to generate a bubble. When using an ink-jet recording method, less noise is generated, and both high-speed printing and multi-color printing are possible.
Conventionally, a water-based ink containing water as the main solvent has been widely employed as an ink employed in such an ink-jet recording method.
In an ink-jet recording apparatus, rubber members are employed in an ink passage comprising an ink tank and an ink-jet head. These rubber members include: a cap which covers the nozzles of the ink-jet head; a wiper which cleans nozzle surfaces of the ink-jet head; a packing seal which is placed at the joint portion between components; a tube which supplies ink from the ink tank to the ink-jet head if the ink tank is provided separately from the ink-jet head; and the like.
However, when an ink for ink-jet recording comes in contact with the rubber members, additives contained in the rubber members are dissolved in the ink. The dissolved additives then precipitate out as insoluble materials, thereby causing problems such as clogging of nozzles of the ink-jet head.
In order to prevent the occurrence of precipitation in an ink, various proposals have been made, such as: adding a chelating agent to an ink; using a maintenance solution containing a chelating agent such as a polyaminocarboxylic acids and the like; and cleaning an ink-jet head with a cleaning solution containing a chelating agent such as ethylenediaminetetraacetic acids and the like.
However, even when the conventional ink, maintenance solution or cleaning solution, each of which contains an common chelating agent, is employed, it is difficult to effectively prevent the occurrence of precipitation caused by contact of the ink with the rubber members.